The invention refers to a self-locking revolute joint, which can be adjusted step by step to an angle by means of pumping movements of an activation lever and is particularly suitable for adjustment of seat height or backrest inclination of vehicle seats. The joint cooperates with a mount, in which a bearing shaft is arranged; with a locking disk, rotatably connected with that arm of the joint which is to be adjusted, having notches at equal angular distances and capable of being rotated around the axle of the bearing shaft; and with a locking element which is movably held onto the mount, particularly rotatably in bearings, having a locking tooth cofunctioning with the notches, being elastically prestressed in the engagement direction of the locking tooth in the direction of one of the notches and having a total of two steering profiles cofunctioning with carriers adjustable by means of the activation lever, each of these having one release profile and one unblocking indentation, the distances of which are adjusted to the angle distance of the notches, whereby a return spring is assigned to the activation lever, prestressing the latter into the central position.
In this adjustment device known from the German Disclosure Document DE-OS No. 34 09 144, the adjustment of the bearing shaft in relation to the mount is achieved by means of turning back and forth, i.e. by pumping movements of the activation lever. The movements are similar to those of a ratchet screwdriver. Thereby, the drive forces are limited to a small angular range of e.g. 15.degree. and can thus be utilized in a space-saving and favorable manner, so that the adjustment device initially mentioned is particularly suitable for revolute joitns to be manually activated.
Normally, the activation lever is in its central position, in which it is held by means of the return spring. In this position, the activation lever does not influence the movements of the locking element, which thus remains in the blocking position due to the elastic force of a spring working on the locking element; the locking element assumes this blocking position independently.
The activation lever may be relatively long, whereby one achieves a great and favorable translation of the adjustment forces, preferably initiated manually. Preferably, it is also bent in a manner that allows a good grip, so that the conditions are ergometrically favorable for the user. In the previously known revolute joint, the activation lever is in two parts; it consists of a coupled rocker which is somewhat longer than the radius of the locking disk, and an actual grip lever. The two parts have a linked interconnection and are held in the extended position by means of a spring. The carriers are arranged on the grip lever proper, the described link connection between the grip lever and the coupled rocker is located in the vicinity of the line connecting the two carriers.